1– Herpes viruses are old. They are ooooooold. Like, hundreds of millions of years old. Specifically, about 400 million years old.
2– Herpes viruses are everywhere. Fish, reptiles, birds, cows, humans, everywhere. And there are lots of different kinds that humans have to deal with– CMV, EBV, HHV-8, VZV, HSV…
3– And, though herpes viruses should not be inserted into the genome of their host cell, generally, some herpes viruses can. Its called ‘strategic somatic genome integration’, and some herpes viruses (and only a small percentage of cells infected with that virus) do insert.
So considering 1), 2), and 3) above, its kinda odd we havent found an *endogenous* herpes virus yet, right? I mean chance + 400 million years = its gotta happen sometime!
A couple things have complicated the hunt for endogenous herpes– the fact many host organisms ‘complete genome’ is not really ‘complete’ and only ‘first drafts’, and the nature of the herpes genomes. They are complicated. So even people specifically hunting for endogenous non-retroviruses, shy away from herpes. It can be an exercise in futility.
One of my favorite labs dug in and finally found some!
In the genome of this ridiculously cute creature:
They found a herpes virus that ‘looks’ like Human Herpes Virus-6 (HHV-6). And not only did they find the virus, they determined the tarsier genome around the virus (as in, it is not a contaminant/mistake, the virus is *in* the tarsier DNA). And, they confirmed the herpes virus was really there themselves, in a different tarsier.
And, like many
specially designed viruses inserted into genomes by our creator viral footprints of evolution in our genome, the endogenous tarsier herpes virus is non functional. Frame-shifts, stop codons, it is no longer the infectious virus it once was. Its just a fossil. In fact some of the characteristics of a HHV-6-like virus were ‘mutated beyond recognition’.
Not only did this lab find the first genuine endogenous herpes virus, they did it with ‘publicly accessible data and open source software’. They needed a good strategy (looking for HHV-6 like elements) and the will to dig through a lot of garbage. That hard work payed off in them getting exactly what they wanted! Herpes!